<!doctype html>
<html>
<head>
<meta charset="utf-8">
<script>
document.addEventListener("DOMContentLoaded", () => {
  document.querySelector("mo").appendChild(document.querySelector("dialog"));
  getSelection().collapse(document.querySelector("template"), 0);
  document.execCommand("delete");
}, {once:true});
</script>
<body>
<dialog>
<template>
</template>
</dialog>
<dl contenteditable>
<li>
<b><progress>
<mo>a</mo>
</progress></b>
</li>
</dl>
</body>
</html>
